Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

650
FXUS63 KLOT 130816
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
316 AM CDT Fri Mar 13 2026

.KEY MESSAGES...

- Very strong and potentially damaging winds with peak gusts to
  around 60 mph will continue through this afternoon. A High
  Wind Warning remains in effect for most of the area.

- There is about a 30% chance for some areas to pick up a
  dusting of snow Saturday morning.

- Waves of thunderstorms may occur on Sunday. There is a Level
  2 out of 5 threat for severe thunderstorms Sunday afternoon
  east of Interstate 55. The primary threat is damaging winds.

- A period of accumulating snow accompanied by northwesterly
  winds gusting over 35 mph may occur Sunday night into early
  Monday.

- A period of cold temperatures is expected Monday and Tuesday,
  with overnight low temperatures ranging from 5 to 15 below
  zero overnight into early Monday morning.

- The period of cold temperatures should be brief with warming
  temperatures by the end of next week.

&&

.DISCUSSION...
Issued at 316 AM CDT Fri Mar 13 2026

Through Saturday:

Early morning regional surface analysis depicts a strong,
wound-up ~986 mb surface low that is chugging its way eastward
across the Upper Midwest. At 0800Z, its associated surface cold
front was still arched back from western Wisconsin into
east-central Iowa, but its fast forward speed has it on track
to enter our western counties a little before sunrise. Looking
aloft, a vigorous shortwave trough evident on GOES water vapor
channel loops is powering its way southeastward towards the
Lower Great Lakes and is pairing up with robust low-level warm
air advection/isentropic ascent to drive a broad swath of
precipitation through the region. In our forecast area, dry air
in the low-levels should keep rain totals under 0.1" with most
precipitation ending before sunrise (though the southern
periphery of a rain/snow band wrapping around the low`s center
could graze some of our northern locales between sunrise and
mid-morning).

It should be no surprise with a mid-latitude cyclone of this
caliber that wind fields are quite strong through the depth of
the troposphere across the region. We`ve already notched several
50+ mph gusts early this morning as the evaporative cooling of
the overnight rain aided in the transfer of momentum from a
screaming 70+ kt low-level jet down to ground-level, and
intermittent 50+ mph south-southwesterly gusts may continue to
be observed at times through remainder the night prior to the
arrival of the aforementioned cold front. Behind the front,
westerly winds should gust more regularly to 50-60 mph during
the daytime today as post-frontal cold air advection steepens
low-level lapse rates and allows us to more easily tap into the
strong 850 mb flow within a more unstable planetary boundary
layer and amidst robust pressure rises. The going wind
headlines for our area thus look to be in good shape, and was
not planning to make any changes to them this morning.

Behind the low/shortwave, a sharp northwest-southeast oriented
low- to mid-level baroclinic zone will get laid out from the
central/northern Plains down through the Ohio River Valley.
Frontogenesis within this baroclinic zone will likely cause an
elongated snow band to develop to our west late tonight. This
snow band would then potentially spread into portions of our
forecast area towards daybreak and continue through Saturday
morning before dissipating or exiting our area to the north and
east. At this time, model guidance suggests that dry low-level
air, somewhat ephemeral frontogenesis, and limited to non-
existent additional forcing support should preclude much more
than perhaps a few streaky dustings of snow accumulation being
observed in our forecast area with this potential snow band.
However, lapse rates are progged to be somewhat steep within the
dendritic growth zone (which should reside squarely within the
cloud layer), and have seen similar f-gen snow events
overperform relative to model guidance, so can`t completely
discount the possibility of up to an inch or so of localized
snow accumulation being observed across a narrow corridor or two
within our CWA.

Ogorek


Saturday Night through Thursday:

This weekend, an upper-level shortwave currently south of
Alaska will undergo significant amplification wile diving
southeastward across the central United States. Ensemble model
guidance is in excellent agreement that the initial surface
cyclone will develop in the lee of the Rocky Mountains near the
WY/SD/NY border region Saturday and rapidly deepen while moving
generally eastward into the Great Lakes Sunday into Monday. In
fact, GEFS/EPS/CMCE all exhibit relatively tight clustering of
path of the low near or directly over northern Illinois or
southern Lake Michigan on Sunday, setting the stage for a
rollar-coaster in weather conditions in our area over a roughly
24 to 36 hour period of time.

As the low deepens while approaching our area Saturday night,
increasing low-level warm air advection will facilitate
temperatures stagnating if not warming through the night. While
the low-level baroclinic zone and a developing warm frontal zone
will be moving northward through time, will have to watch for
any lead subtle shortwave to excite elevated convection or even
an early start to mid-level frontogenesis, especially
considering mid-level lapse rates will be steep. Precipitation
type could favor anywhere from a cold rain to heavy wet snow,
including graupel and hail. For now, will offer a gradient in
PoPs across the area Saturday night ranging from around 20% near
US-20 to around 80% at the Wisconsin State line. This will be a
period to refine going forward.

Low-level warm air advection will only intensify after daybreak
Sunday, allowing for temperatures to skyrocket into the upper
50s (north) to mid 60s (south) in spite of heavy cloud cover. In
fact, impressive pressure falls ahead of the surface low (on
the order of 10mb/6hr) will support strong southerly winds, with
more aggressive mixing profiles supporting widespread wind
gusts of 40 to 50 mph. There is a subtle signal in extended RRFS
and experimental MPAS WRFs for the passage of a mesoscale
gravity wave through the area Sunday morning near the IL/WI
border, which with the continued steep mid-level lapse rates
may support a somewhat unexpected band of storms.

During the late afternoon and evening hours, the surface low
pressure system will move directly overhead or close by. With a
growing signal for a ribbon of low-level moisture to race
northward into our area ahead of the approaching cold front
beneath an intense low-level wind field (850mb flow progged to
increase toward 50kt), am growing increasingly concerned that a
narrow band of low-topped convection may develop and efficiently
transport damaging to destructive winds across the area. At
this point, such a threat appears highest along and east of I-55
where extended CAM guidance supports SBCAPE climbing above 100
J/kg. In scenarios where the surface low verifies deeper and
further northwest, even higher values of instability may
materialize and support a more widespread and potentially higher
impact damaging wind event. For now, the Storm Prediction
Center has introduced a Level 2/5 threat area for severe weather east
of I-55 for Sunday which seems quite appropriate given current
ensemble mean fields.

Sunday night into Monday, the low pressure system will lift
into Michigan as temperatures tumble in our area behind the cold
front. We continue to see a signal for the backside of the
developing comma head snow region to at least graze if not
outright move across our area. Considering strong pressure rises
(on the order of 10mb/6hr) will force similarly strong
northwesterly winds gusting 35 to 45 mph (if not higher), any
falling snow could prove problematic with low visibility and
quick accumulations on roadways. With continued spread in
guidance in the strength, location, and duration of snow on the
backside of the system, as well as generally low probabilities
for at least 6 inches of snow (grand ensemble probabilities are
<50% areawide), did not have enough confidence that warning-
level impacts may be in play to justify hoisting a Winter Storm
Watch with the out going forecast package. (The probability of
"major" or a level 4 out of 5 on the probabilistic WSSI scale is
only 10 to 30% across our area). With that said, can easily
envision the need for a Winter Weather Advisory for parts of the
area Sunday night into Monday if the signal for wintry weather
comes to fruition.

Monday into Tuesday will feature a brief hit of chilly air as
unseasonably cool 850mb temperatures bottoming out near minus 20C
slosh into the region behind the departing storm system. Highs
both days are poised to stay stuck in the 20s. Meanwhile, lows
Monday night are expected to fall into the single digits. With a
continuation of breezy northwesterly winds, wind chills Monday
night are expected to fall to 5 to 15 below zero areawide.
Depending on the actual wind direction, would also expect lake
effect snow to at least graze northwestern Indiana at times, as
well. Thankfully, the polar plunge looks to be short-lived as
ensemble guidance advertises the development of anomalously
strong upper-level ridging and associated warming temperatures
by the end of next week.

Borchardt

&&

.AVIATION /06Z TAFS THROUGH 12Z SATURDAY/...
Issued at 1208 AM CDT Fri Mar 13 2026

A potent storm system will race through the Great Lakes region
through the TAF period leading to inclement aviation conditions
mainly in the form of strong winds.

South to southeast winds at press time are expected to turn
southwesterly over the coming hours as warm air advection-driven
showers sliding overhead force downward mixing of the
increasingly strong low-level wind field via evaporation.
Indeed, do expect surface gusts to increase in magnitude over
the coming hours, with prevailing gusts of 25 to 35kt through
daybreak. Any rain that does reach the surface though daybreak
is not expected to lead to any visby or cig restriction. Cloud
bases should remain above 4000 feet through daybreak.

After daybreak, strong pressure rises on the order of 8mb/6hr
will drive strong westerly winds with sustained winds of 25-30kt
and gusts of 45-50kt. The strongest winds are expected in the
12-20Z window before gradually subsiding through the late
afternoon and evening hours. A band of MVFR stratus based
between 2000 and 3000 ft should spread over the terminals from
daybreak and lift to around 4000 feet this afternoon.

Winds will continue subsiding after sunset and cease gusting
entirely between 02-04Z. In fact, winds may turn nearly calm
toward the end of the TAF Period as a surface high pressure
system builds into the region. Mid-level clouds will thicken
tonight in advance of the next storm system developing over the
central US.

Borchardt

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...High Wind Warning until 4 PM CDT this afternoon for ILZ003-
     ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-
     ILZ019-ILZ020-ILZ021-ILZ023-ILZ103-ILZ104-ILZ105-ILZ106-
     ILZ107-ILZ108.

     Wind Advisory until 6 PM CDT this evening for ILZ032-ILZ033-
     ILZ039.

IN...High Wind Warning until 4 PM CDT this afternoon for INZ001-
     INZ002-INZ010-INZ011.

     Wind Advisory until 7 PM EDT this evening for INZ019.

LM...Storm Warning until 4 PM CDT this afternoon for the IL and IN
     nearshore waters.

     Gale Warning from 4 PM this afternoon to 10 PM CDT this
     evening for the IL and IN nearshore waters.

&&

$$

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